(9) a compound as described in (1) above, wherein P is a group of the formula: in which Z is ##STR4## in which either bond may be bonded to B, or a bond; and B is ##STR5## in which a is an integer of 0 to 2, b is an integer of 0 to 2 and c is an integer of 1 to 5, or (ii) a bond, excepting the case where Z and B both are a bond, (10) a compound as described in (9) above, wherein Z is ##STR6## in w